Technical Abstract:
Infection with Campylobacter is the leading bacterial cause of human food-borne gastrointestinal illness. As part of the National Antimicrobial Resistance Monitoring System (NARMS), Campylobacter has been tested for susceptibility to eight antimicrobials (azithromycin (Az), chloramphenicol (Cl), ciprofloxacin (Ci), clindamycin (Cm), erythromycin (Em), gentamicin (Gm), nalidixic acid (Na), and tetracycline (Tc)) since 1998 using the Etest (ABBiodisk) and speciated by PCR. From 1997 through 2003, the majority of the isolates were C. jejuni (range 55-77%) while the remaining isolates were C. coli (range 33-45%). No resistance was observed to chloramphenicol or gentamicin for either species in any year. For each year, overall resistance in C. coli was higher than in C. jejuni. Multiple resistance (MR), defined as resistance to greater than or equal to 2 antimicrobials, among C. jejuni varied from 11.5% in 1999 to 23.4% in 2001. The majority of these MR isolates were resistant to 2-3 antimicrobials with CiNaTc and CiNa the first and second most common MR patterns, respectively, for C. jejuni. MR among C. coli ranged from 26.2 to 47.7% of the isolates throughout the same years with resistance to CiNaTc (8.6%) and AzCmEmTc (2.9%) the most frequently observed patterns. Interestingly, analysis by antimicrobial class (versus individual antimicrobials) indicated that less than half (10.9%) of MR isolates from 2001 were resistant to, greater than or equal to 2 antimicrobial classes. The distinct differences observed between C. jejuni and C. coli isolates require further investigation.